hugetlbfs: do not call user_shm_lock() for MAP_HUGETLB fix

Commit 6bfde05 ("hugetlbfs: allow the creation of files suitable for
MAP_PRIVATE on the vfs internal mount") altered can_do_hugetlb_shm() to
check if a file is being created for shared memory or mmap().  If this
returns false, we then unconditionally call user_shm_lock() triggering a
warning.  This block should never be entered for MAP_HUGETLB.  This
patch partially reverts the problem and fixes the check.

Signed-off-by: Eric B Munson <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Adam Litke <[email protected]>
Cc: David Gibson <[email protected]>
Cc: Lee Schermerhorn <[email protected]>
Cc: Nick Piggin <[email protected]>
Cc: Hugh Dickins <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

fs/hugetlbfs/inode.c

@@ -936,15 +936,9 @@ static struct file_system_type hugetlbfs_fs_type = {
 
 static struct vfsmount *hugetlbfs_vfsmount;
 
-static int can_do_hugetlb_shm(int creat_flags)
+static int can_do_hugetlb_shm(void)
 {
-	if (creat_flags != HUGETLB_SHMFS_INODE)
-		return 0;
-	if (capable(CAP_IPC_LOCK))
-		return 1;
-	if (in_group_p(sysctl_hugetlb_shm_group))
-		return 1;
-	return 0;
+	return capable(CAP_IPC_LOCK) || in_group_p(sysctl_hugetlb_shm_group);
 }
 
 struct file *hugetlb_file_setup(const char *name, size_t size, int acctflag,
@@ -960,7 +954,7 @@ struct file *hugetlb_file_setup(const char *name, size_t size, int acctflag,
 	if (!hugetlbfs_vfsmount)
 		return ERR_PTR(-ENOENT);
 
-	if (!can_do_hugetlb_shm(creat_flags)) {
+	if (creat_flags == HUGETLB_SHMFS_INODE && !can_do_hugetlb_shm()) {
 		*user = current_user();
 		if (user_shm_lock(size, *user)) {
 			WARN_ONCE(1,